Digital apparatus for the timing and analysis of internal combustion engines

ABSTRACT

A starting impulse generated when the crank shaft of an engine passes a specific point and starts a counter that counts impulses for one revolution. During the same revolution, another signal corresponding to a specific engine event starts another counter that continues until the end of the same revolution. A computing circuit uses data from the counters to determine engine speed and the angle at which the engine event occurs and presents this information as a numerical readout. A mark signal may be generated as a cursor for cathode ray tube display of ignition or other engine waveforms. The cursor can be moved to any point along the waveform by a manual control, and the angle at whatever point is selected will be presented in the numerical readout.

United States Patent [1 1 Eberle et al.

[4 1 Mar. 11, 1975 DIGITAL APPARATUS FOR THE TIMING [54] 3,594.552 71971 Adamson 235/92 CV AND ANALYSIS OF INTERNAL COMBUSTION ENGINESPrimary Examiner-Gareth D. Shaw Assistant Examiner-Robert F. Gnuse 7 l tA th Eh I 5] nven Ors g z g f g g t gl g Attorney, Agent, orFirm--Curtis, Morris & Stafford of Ohio 1 [73] Assignee: Columbia GasSystem Service [57] ABSTRACT Corporation, Columbus, Ohio A startingimpulse generated when the crank shaft of [22] Filed, Apr 26 1973 anengine passes a specific point and starts a counter that counts impulsesfor one revolution. During the DM- 349 same revolution, another signalcorresponding to a specific engine event starts another counter thatcon- [52] U S C] 235/92 FQ 235/92 C 235/92 CC tinues until the end ofthe same revolution. A comput- 235/92 235/92 ing circuit uses data fromthe counters to determine [5 1] Int Cl i103! 21/34 engine speed and theangle at which the engine event [58] Fie'ld CP 92 FQ occurs and presentsthis information as a numerical 235/92 readout. A mark signal may begenerated as a cursor for cathode ray tube display of ignition or otheren- [56] References Cited gine waveforms. The cursor can be moved to anypoint along the waveform by a manual control, and UNITED STATES PATENTSthe angle at whatever point is selected will be presgfig gkgzggrakybrook 235/92 CV ented in the numerical readout,

,l c er 3,263,065 7/1966 Savage 235/92 CC 20 Claims, 8 Drawing FiguresFREQuEMcY PER/OD GATE ScALER COUNTER /5 g l 250 KHz J CRYSTAL CLOCK l I/5 22 I Z3 24 ,L I r i r I GATE FREQUENCY up LIP-DOWN ScALER COUNTER l ll L- 1 II 20 Mum/WON COMPuTEpEQuENQE START WMING CONTROL. PULSE LOG/cCOMPUTE SEQUENCE END GN/T/ON PULSE /9 MARK PuLsE GATE Z6 Z7 M PK .SINGLE01v OFF 012 Z8 4-PERIOD AVERAGE Z E MANUAL. 4 CYCLE ENG/NE ENG/NEPATENTEB 1 I975 3. 870.869

SHL'EI l U? 6 Hzzausmy PER/OD GATE ScALER COUNTER F i i 250 KHz J cmsmz.I

CLOCK Z ZZ 24 i J I G fihsaumcv up LIP-DOWN SCALE/2 COUNTER i L i H F ZQWM'WG g m COMPUTE [fizoumvcls START ONTROL. puLSE LOG/C Com/ un:SEQUENCE END 1 A 34 Z! IGN/T/ON /8 /9 MARK PULSE GATE q /Z5 J26 Z7 M RKSINGLE ON OFF I OR AVERAGE Z C Z I- MANUAL 4 CYCLE PATENTEDHARI I I9753.870.869 SHEU 2 [1F 6 34 DATA REG/5T5? COMPUTE COMPUTE SEQUENCESEQUENCE 3600 START END SELEC- T012 3/ I I7 I 5 %5 5 ON ETE PEQ/ODCOUNT/5Q I LOG/C i TOf? I I I I 9 i 2 I BINARY UP-DOWN 5 722. RATE :DOWNCOUNTEQ MULTIPLE I I I 38 I 39 l FREQUENCY OUTPUT 5cAI EI2 COUNTER ANGLE1 SPEED ANGLE M EMOQY 5 PEED I A I DATA FQEAD ADDRESS 5PEE0 DATA 72ENG/NE SWEEP GENERATOQ PATENTEDHARI 1 I975 3.870.869

SHEET 3 OF 6 43 SDPEED 5 4/4 ATA PEED RESET 4 CYCLE FROM COUNTER FROMENG/NE COMDUTEF? COMPUTER TIMING 0360 Q 46 CONTROL PULSE 360- 720 SPEEDLOAD LOG/C 7 52 REG/STEP? 65 V 5 45 VRESET y I 250 MH BINARY v SWEEPENG/NE cRvsTAf RATE E X EEF CONT/20 SWEEP CLOCK MULTIPLIER COUNTERUNBLANKING 4 L/OGIC ENG/NE 59 r 54 W i /6c. BLAN I q 3 655%? DAG 02 5. 7SIGNAL.

REFERENCE CONVERTER 6/ v [DANE/L A AL ENGINE FRONT VOLTAGE hfii 5WEEPCONTQOL 57 IQAMP 58 VOLTAGE COMPARATOR 7 PULSE G NE ATO;2 B S;

PATENTED HARI l IQTS SHEET b 0F 6 SWEEP TRIGGER r SELECT 5WEEPIOIv/T/OIv 5ELECTOR OR WMING 5W'TCH 65 64 67 gg 6 9 74 gELETED WE D g ftSELEC- RAMP 5WEEP RAMP 77 AT PTs E f E f; DEFLECTION 56 R Em AMPLIFIERT1 [1.4 72 VOLTAGE I COMPAPATOR+ gELECTED E72 76 E TEZ ea- 5 WEEDCONTROL LOG/C RAMP TO EEFLECTION .MPLIFIERS ANGLE/SPEED ANGL$PEED/4O A ADATA I MEMORY 5 QEAD CE I. Tlg- 5CDATA ADDRE5$ UNBLANKING ANNER DATA 6 vI I I 50 7 I 3 Z MHE DSPLAV SEGMENT DIG/T AAOLE/S/ EED 3 55 COUNTERvCOUNTEQ SELECTOR 82 8;] V CNOR/z. I HARACTOQ gu/I/IEQIcs NUMEg/cs IDISPLAY WAVEF'ORM NABLE WAVEFORM D/G/T/ZER w GENERATOR 88 I VERTCHARACTOR I WAVEFORM PIIEIIIEII I I m 3.870.869

SHEET 5 [1F 6 TRACE I SELECT I I- 5 OR A MULTIPLEY MODE. CI-IoP ORALTERNATE swap ELECTOR 99 WITCH I 532% \5AMPLEA SAMPLE A5 75 HORIZ.DISPLAY 5 MPLE CONTROL DEFLECT/ON AMPL/FEQ GENERATOR LOG/C 5ELEcTED-5WEEP /O/ I 4 TRIGGER 77Q/GGER IGNITION C/Rcu/T pULsE /06 INPUT 96ATTENUATOR PREP i TRACE A AMPLIFIER v 9/ INPUT V/RAEE B I Q I //ZATTENuATvR PRE- AN O DEELEET/ON "(Z TRACE B AMPLJFIER GATE AMPLJ/ /ER 94COMPOSITE I 97 VERT SAMPLE VEFLECTION AvEEoRM N Q To VERT ANALOQCHARACTOR I GATE WAVEFORM PATENTEU m1 1 I975 COMPOSITE DEFLECTIOA/AMPL/F/ER WA VEFORM 2 C I.

Tiq E mz UNBLAN KNG SHEET '6 IF 6 A SAMPLE A FROM VER DEFLECTION AMP.

x 6 SELECTED ANAL-0G SWEEP GATE //8 RAMP H7 INVERTER IZZ r H0212. kANAL-0G CHARACTER GATE /Z/ WAVEFORM /3/ 5WEEP 551.50 DATA 7 /Z4 7Z2AcESELEcT DATA /25 EAST Sweep UNDLAN UNBLANKING /Z6 'MARIC Puma: /z9 1SINGLE/NORMAL. V B3 TRALZE CONTROL. L m,

AMPLIFIER BACKGROUND OF THE INVENTION This invention relates to thefield of analyzers for internal-combustion, piston engines, and inparticular, it relates to the field of analyzers with digital readout ofspeed and angular information. I

Most commercially available engine analyzers heretofore have merelyindicated the waveform of ignition pulses by means of a conventionalOscilloscope with special probes. In general, they are not suitable foraccurately timing an engine nor for use with condenser dischargeignition (CDI) systems. Also, with multicylinder engines, it is possibleto time the No. l cylinder correctly and yet have an error of severaldegrees on other cylinders. On large engines timing often takes twopeople: one to read the timing light and another to adjust the angle,for the timing marks and the ignition.

advance adjustment are often at opposite ends of the engine. Convenientand safe access to the timing marks is also often a problem.

One object of this invention is to provide an instrument that can beeasily connected to an engine and, using digital circuits, will directlyread timing advance angle to a high degree of accuracy. It has beenproposed to control an analyzer by a stable but variable oscillator at3,600 times engine speed. By gating a counter on and off with a magneticpick-up positioned on the engine flywheel to detect top center, it waspossible to set the oscillator at 3,600 times engine speed. This, ineffect, divided the flywheel into 3.600 equal increments, eachcorresponding to 0.1 degree of crank angle. When this was done, the samecounter was reset and used to count the oscillator pulses between theignition pulse and top center. This was the timing angle in degrees andtenths. That system had several disadvantages. However, it was possibleto time an engine without a timing light. It was also proposed to use avoltage controlled oscillator and phase lock it to the variations'inengine speed.

A disadvantage of the timing method just described is that the enginespeed can vary slightly from the calibration rotation to the measurementrotation.

Therefore, another object of this invention is to provide an analyzerthat calibrates and measures during the same rotation.

BRIEF DESCRIPTION OF THE INVENTION In accordance with this invention, acontrol circuit, actuated by a signal that occurs when the crankshaftreaches a specific position, such as the top dead center (TDC) of theNo. 1 cylinder, allows fixed frequency pulses to be counted in a firstcounter until the next occurrence of the timing pulse. While the firstcounter is counting, the same pulses are gated through to a secondcounter starting with the occurrence of a signal that corresponds intime to a specific engine event, such as an ignition pulse for aspecific cylinder, the timing of which is to be investigated. The secondcounter stops counting at the same time as the first. The total count inthe first counter. is related to the speed of the engine, and the totalcount in the second counter, is related to the angle between thecrankshaft position at the time of the signal being investigated and theposition that corresponds to the timing pulse.

.2 After this pulse information has been stored in the counters, theangle and speed are computed. The angle is computed by causing acounter, for example the second counter, to count a selected numberequal to that originally counted in the second counter. However, the

counting rate during computation is at a pulse repetition frequency thatis a certain fraction of the clock pulse frequency at which the countingwas first done. The fraction is proportional to the total value countedin the first counter and to the clock pulse frequency. The fractionalrate is typically produced in a binary rate multiplier and is appliedtoa down terminal of the second counter to count the number stored thereinback to zero. While the second counter is counting to zero, a thirdcounter is counting up from zero at a clock frequency. When the secondcounter reaches zero, the counting stops in the third counter and thecount therein is transferred to the second counter, which is then causedto count again back to zero at the clock frequency. During this secondcount-down, the third counter is caused to count up at yet another rate,such that the final number on the third counter, when the second counterhas returned to zero the second time, is exactly the number of degreesand decimal fraction of a degree between the crankshaft position at thetime of occurrence of the specific engine event and the position of thecrankshaft at the next timing pulse. This number is transferred to astorage device, leaving both the sec-ond and third counters clear.

The speed is calculated by loading a specific scaling constant into acounter, preferrably the second counter, and counting that number downto zero at a counting rate that is a fraction of the rate at which theoriginal counting was done. This fraction is proportional to the rate atwhich the second counter was counted back to zero the first time. At thesame time that the second counter is being counted from the specificnumber back to zero, the third counter is counting up from zero at adifferent rate, and the relationship between the counting rates is suchthat, when the second 'counter reaches zero, the number recorded in thethird counter is equal to the speed in RPM of the crankshaft of theengine. I

The information thus determined for the speed and angle can be enteredinto a numerical display unit. In particular, it can be entered into asystem that will deflect the electron beam of a cathode ray tube totrace out numbers on the screen, and these numbers can be viewedsimultaneously with the'waveform of the ignition or other enginecharacteristic under investigation so that analysis of the engineincludes angle and speed information along with waveform information,all capable of being viewed virtually simultaneously.

It should be noted that different clock frequencies can be used atdifferent times. The following description will be made in relativelyspecific terms because it would be exceedingly complex to spell out oneach occassion the possible variations, but such variations are withinthe contemplation of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of thecomponents used in obtaining the basic data according to the invention.

FIG. 2 is a block diagram of the components used in computing speed andangle according to the invention.

FIG. 3 is a block diagram of a system for generating a marker pulseaccording to the invention.

FIG. 4 is a block diagram of a sweep generating system as used with thesystem of this invention.

DETAILED DESCRIPTION OF THE INVENTION Data Acquisition Phase Within theanalyzer, information is processed in two phases. In the first phase,data acquisition, two time intervals are measured automatically. Duringthe second phase the measured data is processed by a special purposecomputer for display. During the data acquisition phase, the crankrotation period is measured by the circuit shown in FIG. 1. Measurementof the crank rotation period begins with an acquisition control logiccircuit 11, which may comprise a flip-flop circuit receives, by way ofan input terminal 12, a timing pulse generated by any suitable means 13and usually fixed so that it occurs when the No. 1 piston is at top deadcenter (TDC) position. This timing pulse causes the acquisition controllogic circuit 11 to open a gate 14 by causing the flip-flop to changestates. A fixed frequency clock 15, for example a crystal oscillatorhaving a frequency of 250 KHZ, is connected to supply pulses at thisfrequency to the gate 14. The pulses that pass through the gate areapplied to a frequency scaler 16 through which they may pass at the samefrequency or at a frequency that is a fraction of the initial frequency.The pulses from the frequency scaler are applied to a first countercircuit 17 which is referred to as a period counter. When the second TDCpulse is received, the acquisition control logic circuit 11 closes thegate 14 so that no further pulses can pass through it to the counter 17.At that time the count n, stored in the counter 17 is proportional tothe time required for thecrankshaft of the engine being analyzed tocomplete one revolution.

During the same revolution, a second pulse, which may be obtained fromthe ignition circuit via an input terminal 18, or a mark pulse generatedin another portion of the analyzer and applied via an input terminal 19,is selected by a selector gate 21, which may be asingle-pole-double-throw switch, and transmitted to the acquisitioncontrol logic circuit 11. The acquisition control logic circuit usesthis latter pulse, for example in a second flip-flop circuit, to open asecond gate 22, which then passes pulses from the clock to a secondfrequency scaler 23. The frequency scaler may pass the pulses at thesame repetition rate or may divide them by an integral number. Theoutput of the frequency scaler 23 is applied to the up count terminal ofan updown counter circuit 24. This counter counts pulses from the timeof the occurrence of the ignition or mark pulse to the time ofoccurrence of the second TDC pulse, which closes the gate 22 as well asthe gate 14. Thus, on one crank rotation two time intervals aremeasured, the time T from one TDC to the next and the time r from theignition or mark pulse, as selected by a manual control 25, to thefollowing TDC.

There are several modes of operation of the data acquisition phase. Theinstrument can be used on two cycle or four cycle engines by actuatingmanual selectors 26 or 27, respectively. If a four cycle engine is to beanalyzed, time measurements are made only during those crank rotationsin which ignition or mark pulses occur. For a two cycle engine,measurements can be taken during any crank rotation. The operator mayalso select single or four period average measurements. In the singlemode clock pulses pass through to frequency scalers l6 and 23 unchangedand time measurements are taken in a single crank rotation. If a fourperiod average is selected, the total count of four revolutions ifscaled by four by the frequency scalers 16 and 23. In effect the scalersapply the average of four measurements to the counters. The latter modeis advantageous when engine timing or speed is somewhat erratic.Although the computer circuitry automatically resets the counters whenrequired, the operator may manually reset and restart the system from areset button 28 lo cated on the instrument panel. An additional controlis provided permitting the operator to selecteither the ignition pulseor the mark pulse. Selection and use of the mark pulse is describedhereinafter.

COMPUTATION PHASE At the conclusion of the acquisition phase, theacquisition control logic circuit 11 sends a compute sequence start"signal through an output terminal 29 to a computation section shown inFIG. 2. The compute sequence start signal is applied to an inputterminal 30 of a computer control logic circuit 31. During thecomputation phase the acquisition control logic circuit 11 is quiescent,and upon completion of the computation phase, a compute sequence endsignal" is generated by the compute control logic circuit 31 andtransmitted via an output terminal 33 to an input terminal 34 of theacquisition control logic circuit 11 in FIG. 1 to reactuate the dataacquisition phase and cause new measurements to be taken. The alternateacquisition and computation process is repeated as long as theinstrument is connected to the engine under test.

In the computation phase, information accumulated in the period counter17 and up-down counter 24, both of which are also shown in FIG. 2, isprocessed into advance angle and engine speed. This is a three stepserial process in which two steps are required to obtain the advanceangle and one step for engine speed. The basic information is that count11, stored in the period counter during one complete revolution is to360 as the count n stored inthe up-down counter is to the advance anglea. Or:

For the speed, a count N is obtained that is simply:

where k is a constant.

Upon receipt of the compute sequence start pulse, the computer controllogic circuit 31 causes the number 11,, accumulated in the periodcounter 17, to be stored in the data register 34. This can be done byhaving the data register 34 non-destructively read the accumulated countin the counter 17. A binary rate multiplier 36 has one of its inputterminals connected to the counter 17. The count stored in the counter17 is presented as a parallel binary number. A second input to thebinary rate multiplier 36 is a clock signalf from a clock 35, which canhave a different frequency than the clock in 'FIG. 1. It is convenientfor the frequency f, to be much higher, for example 1 MHz. The outputsignal of the binary rate multiplier 36 is a pulse signal given by theequation:

where n is the parallel binary number presented to the rate multiplier,n,,, is the maximum value n can have, as determined by the ratemultiplier, and f is a' clock signal.

At this time in the computation sequence the output of the ratemultiplier 36 is:

where n, is the number accumulated in the period counter 17 and isproportional to the crank rotation period, and n, is the maximum numberthat can be accumulated in the period counter. For an 18 bit counter,n,,, 2 -1=262,l43. The computer control logic 31 causes f to be routedthrough a reversing gate 37, which is basically a doublepole-double-throw switch, to the down clock input of the up-down counter24. The clock signal f, is routed through a frequency scaler 38unchanged to an output counter 39.

The up-down counter 24, which contains the n information, counts downuntil zero is reached at which time the counting is stopped. The time I,required for the up-down counter 24 run-down is:

While the up-down counter 24 is counting down at the rate f,, the outputcounter 39 is counting up at the rate 1, and during the time t itaccumulates the count n where:

It can be seen that a quantity proportional to n /n has been computed.

During the second step of the computation process the number n;, in theoutput counter 39 is parallel loaded into the up-down counter 24 and theoutput counter 39 is cleared. The period counter 17 is cleared andloaded with the number 3,600 from a data selector 41, which isessentially a single-pole-double-throw switch. This establishes anoutput f from the binary rate multiplier 36 where:

m 3600n /n Since the output counter 39 counts in binary coded decimaL mis the advance angle in tenths of a degree. The error in the aboveprocess is within fl.2. The advance angle number n. in the outputcounter 39 is then loaded into an angle/speed memory circuit 40 forfuture display. All counters 17, 24 and 39 are cleared and the computercontrol .logic circuit 31 proceeds to the third computation step.

The third and final computation step results in engine speed in RPM. Thedata selector 41 connects the data register 34 in which count n has beenpreviously stored, so that n, is parallel loaded into the period counter17. The output frequency of the binary rate multiplier 36 is: r

. gine under test.

fl l m fr A scaling constant 5722 is parallel loaded into the updowncounter 24, and the computer control logic circuit 31 causes the signalf to be routed through the reversing gate 37 to the down clock input ofthe up-down counter 24. The number 5722 is determinted by theequationz'l RPS RPM K n,,,/f Since the data acquisition clock 15 in FIG.l has frequency of 250,000 pulses/second, and n is 262,143. K=57.22.Since the computation is on a fixed point basis, K=5722 is loaded intothe counter 24. The 1 MHz clock signal is routed through the reversinggate 37 to the frequency scaler signal 38 where f, is divided by andapplied to the output counter. The up-down counter 24 down counts from5722 to 0 in a period of time t During the time interval t the outputcounter 39 is counting up. When the up-down counter 24 reaches 0counting process ends. The contents of the output counter n is the speedin RPM:

The speed data is then loaded into the angle-speed memory for futuredisplay.

At the conclusion of the third step all counters 17, 24, and 39 arecleared and the compute sequence end pulse is issued to the acquisitioncontrol logic circuit 11 in FIG. 1. New data is acquired processed, andrepeated as long as the instrument is connected to the en- Engine Sweepand Mark The purpose of the engine sweep is to provide a horizontalsweep rate proportional to crank rotation to display ignition and otherwaveforms on a cathode ray tube. A mark, appearing as a small brightspot in the cathode ray tube, is used to identify points of interest onthe display in terms of crank angle. When the mark is not in use theangle computed and displayed is the ignition advance angle. When themark is used, its position is controllable from the instrument panel andthe angle computed is the advance angle of the mark referenced to thetiming pulse.

Development of the engine sweep begins during the third step-of thecomputation phase in which engine speed is computed. While the outputcounter 39 is accumulating the speed count in RPM, a second outputfrom'the frequency scaler 38 is providing speed data through a terminal42 to the engine sweep section shown in FIG. 3. This speed data is aburst of clock pulses having a frequency scaled to f /20 and isconnected by an input terminal 43 to a speed counter 44, which isaccumulating a number porportional to engine speed. After thisaccumulation the number in the speed counter 44 is parallel loaded intoa speed register 46. The speed counter is then reset in preparation forthe next accumulation.

The contents of the speed register 46 is connected to a binary ratemultiplier 47 along with a train of clock pulses, from the 250 KHz clock15 to produce an output signal having a frequency f As a result ofrepeated speed computations and accumulations in the speed counter 44,the contents of the speed register 46, and therefore the frequency f,,is maintained proportional f,/9 by a frequency scaler 48 and is appliedto a sweep control counter 49. The timing pulses which occur once foreach engine crank rotation are also applied to the counter 49 through aninput terminal 51 to reset it. Between timing pulses the sweep controlcounter 49 is accumulating a count at a linear rate. At any instant oftime the contents of this counter is proportional to crank anglereferenced to the timing pulse. Between timing pulses the cathode raytube is unblanked. If the instrument is connected to a 4-cycle engine,the operator may select -3 60 or 360-720 by means ofa control 52. Thispermits viewing of either the first 360 or the second 360 of crankrotation. This is accomplished by the engine sweep unblanking logiccircuit 53.

Digital information from the sweep control counter 49 is continuouslyapplied to a digital-to-analog converter 54 where a staircase typewaveform is produced. This waveform consists of 510 successively highervoltage steps. This signal passes through an analog scaling circuit 56where it is scaled and smoothed into a linear ramp, or sawtooth,waveform to produce, at an output terminal 57, the engine sweep.

The mark is produced from the engine sweep ramp applied to a voltagecomparator 58. A second voltage, generated in a reference source 59 andadjustable from a front panel control 61, is also applied to the voltagecomparator 58. When the difference between the two voltages is zero apulse generator 62 produces the mark pulse at an output terminal 63.When the mark is being used, the mark pulse is substituted for theignition pulse and the computed and displayed angle is the advance anglemeasure from the timing pulse to the mark.

Scaling of the engine sweep may be changed by a front panel control ofthe scaling circuit 56. The operator may select a horizontalmagnification of six times normal. This This permits viewing any 60sector of the crank rotation. Use of horizontal magnification and themark permits the operator to identify in degrees of crank angle anypoint of interest on the cathode ray tube trace. K

Fast Sweep Generator When the engine sweep is not employed, the fastsweep generator shown in FIG. 4 may be selected. This generator producesa fast linear time base for observing such phenomenon as primary orsecondary ignition waveforms.

Fast sweep ramps are initiated by trigger pulses. The trigger source maybe either ignition pulses applied to a terminal 64 or timing pulsesapplied to an input terminal 66, depending on the setting of a control65. The selected trigger pulses pass through the selector gate 67, whichis basically a single-pole-single-throw switch, and set an RS flip-flop68. The low-going output of the flip-flop 68 permits a capacitor in aramp generator 69 to charge at a linear rate. The rate at which itcharges is controlled by a sweep selector switch 71 located on theinstrument panel.

A reference voltage is applied through an input terminal 72 to a voltagecomparator 73, and the output of the ramp generator 69 is also appliedto the same comparator. When the ramp voltage equals the referencevoltage, the voltage comparator resets the flip-flop 68 and thecapacitor is discharged. At this time the generator is ready for thenext trigger pulse which starts the process over again. A sweep selectcircuit 74 in conjunction with the sweep selector switch 71 provides ameans for selecting either engine sweep, via the terminal 76, or fastsweep. The selected sweep is routed through an output terminal 77 to thehorizontal deflection amplifier.

Digital Display Generator The digital display generator in FIG. 5provides two functions: multiplexing of all information displayed on thecathode ray tube, and the generation of digital display waveforms. Adisplay multiplex control 79, which is essentially a 3-position switchand is driven by the 250 KHz clock 15, sequentially controls thegeneration of the numerics waveforms and the sampling of the verticalinputs, trace A and trace B. A segment counter 81 clocked by the displaymultiplex control provides three bit binary number to control theoperation of a numerics waveform generator 82. This circuit generatesthe vertical and horizontal deflection waveforms required to produce theseven number segments on the cathode ray tube. The three hit number alsoaddresses a data scanner 83 where data from the angle/speed memory 40 isconverted to the cathode ray tube unblanking waveform. A clock pulsefrom the segment counter 81 up-dates a digit counter 84, which, aftereach count of 4, updates an angle/speed selector 86. The contents of thedigit counter 84 and angle/speed selector 86 provide the read addressfor the angle/speed memory 40. This read address is also applied to adisplay digitizer 87 in which analog gates apply stepping voltages viaan output terminal 88 to step the digits sequentially across the face ofthe cathode ray tube. The vertical deflection voltages for numerals aresupplied from the numerics waveform generator 82 via an output terminal89.

Vertical Deflection Amplifier The vertical deflection amplifier in FIG.6 provides the necessary signal amplification and control to move theelectron beam vertically in the cathode ray tube. Instrument inputwaveforms, trace A and trace B, received at terminals 91 and 92 passthrough their respective attenuators 93 and 94 and preamplifiers 96 and97 where deflection scaling in volts per centimeter is accomplished. Acontrol logic circuit 98 may operate in either oftwo modes. In themultiplex mode, sampling pulses from the digital display generator viainput terminals 99 and 101 cause a rapid sequential sampling of trace A,trace B, and the vertical character waveform. In the alternate mode,trace A is displayed completely followed by trace B and digitalinformation is painted in a time interval between traces. A sweepselector switch 102 establishes the control logic mode. A trace selectswitch control 103 on the instrument panel permits selection of trace Aonly, trace B only or both traces. An ignition pulse is developed fromthe trace A signal by a trigger circuit 104. This pulse is appliedthrough a terminal 106 to both the computer and the fast sweep logic.The sequential deflection signals as assembled by analog gates 107-109pass through a deflection amplifier 111, where final amplificationprovides the necessary deflection signal to an output terminal 112.

Horizontal Deflection Amplifier FIG. 7 shows the horizontal deflectionsection in which signals representing sampling of trace A and trace Bare applied through an input terminal 114 to an sweep ramp is applied byway of another input terminal 118 to the analog gate 116, and the gateoutput signal is connected to deflection amplifier 119.

At specific times the electron beam has tobe defiected to trace outnumerical characters, and signals for this purpose are applied to aninput terminal 121 from which they are connected to another analog gate122. The gating signals are obtained from the inverter 117, and thegated output signal is connected to the deflection amplifier 119. Theoutput of the amplifier 119 controls horizontal deflection of thecathode ray tube beam.

Unblanking Control The unblanking circuits in FlG. 8 combine unblankingsignals applied to terminals 124-l29 and conditions necessary to turn onand off the cathode ray tube beam. There are two modes of operation.During the normal mode, an unblanking combinational logic circuit 131combines un'blanking pulses from the fast sweep, engine sweep and datadisplay generator circuits with sweep and trace select conditions. Atrain of pulses of proper widths and timing are amplified by anunblanking amplifier 132 which causes the cathode ray tube beam to begated on and off. The mark pulse, described previously, is also appliedand when processed through the circuitry, causes a higher beam currentto occur during mark pulse time. This results in an intensified spot onthe cathode ray tube traces. A second mode of operation is providedpermitting the instrument operator to disable the unblanking circuits.Upon depressing a spring loaded switch located on the instrument panel,an unblanking control 133 will actuate a single trace logic circuit 134to cause a one complete paint of all traces and digital data on thecathode ray tube. This mode is employed during photography when apermanent record of the total display is desired.

What is claimed is:

1. Digital analyzing means for a rotating body, said 4 means comprising:

A. clock signal source means to produce fixed repetition rate clocksignals;

B. a first counter;

C. first connecting means to connect said first counter to said sourcemeans to count a first number :1 of said clock signals at a repetitionrate off while said body-rotates through a first angle;

D. a second counter;

E. second connecting means to connect said second counter to said sourcemeans to count a second number in of said clock signals at a rate of kfproportional to the repetition rate f while said body rotates through asecond angle;

F. first signal generating means'connected to said clock signal sourcemeans to generate a first signal having a repetition rate f proportionalto the repetition rate f and to said-number n, and inverselyproportional to a maximum count .n,,,;

G. means connected to said first signal-generating means to count aselected number a atsaid repetition rate f to establish a first timeinterval t, n /f,;

H. second signal-generating means connected to said clock signal sourcemeans to generate a secondsignal having a repetition rate f2; and

l. means connected to said second signal-generating means to count fromzero to a number n at a rate f for said time 1 such that n, t f is ameasure of angular rotation of said rotating body. 1

2. The analyzing means of claim 1 in which said first connecting meanscomprises:

5 A. means to generate a timing pulsesignal each time said rotating bodypasses a predetermined angular position; and

-B. gating means opened by selected ones of said timing impulse signalsand closed by the succeeding timing impulse signal, whereby said firstangle is 360.

3. The dig-ital analyzing means of claim 2 in which 4. Thedigitalanalyzing means of claim 3 in which f I/ mfc- 5. The analyzing means ofclaim 2 in which said selected number n,-, is 60f /n and said rate f isproportional to the rate f whereby said number 11 is the num; ber ofrevolutions per minute of said body.

6. The analyzing means of claim 5 in which said means to count from zeroto a number n comprises a sealer circuit having a scaling ratio r,whereby f =f /r.

7. The analyzing means of claim 6 in which r=l00.

8. The digital analyzing means of claim 5 in which said means to count aselected number n;, comprises said second counter and said means tocount from zero to a number n comprises a third counter.

9. The digital analyzing means of claim 8 in which said second counteris an up-down counter comprising means to parallel-load said number ntherein.

10. The digital analyzing means of claim 2 in which:

A. said second connecting means comprises second gating means that opensat a particular point in a revolution of said body to start the count ofn at a particular engine event and closes simultaneously with saidfirst-named gating means;

B. n =n and 11. The digital analyzing means of claim 1 in which n =nand-f is proportional to 3600]} and inversely proportional to n,,,,whereby said number 11 is a measure of the angle through which said bodyrotates while said second counter is counting n 12. The digitalanalyzing means of claim 1 in which said first signal-generating meanscomprises a binary rate multiplier having a maximum count it, higherthan any number n or 3600 to be entered into it.

13. The digital analyzing means ofclaim 12 in which:

A. said first connecting means comprises:

1. means to generate a timing impulse signal each time said rotatingbody passes a predetermined angular position, and

'2. first gating means opened by selected ones of said timing impulsesignals and closed by the succeeding timing impulse signal, whereby saidfirst angle is 360;

B. said second counter is an up-down counter comprising an up inputterminal and a down input terminal; and

C. said second connecting means comprises second gating means opened ata time corresponding to a selected event during a rotation of said bodyand closed simultaneously with said first gating means and connectingsaid clock signal source means to said up input terminal.

14. The digital analyzing means of claim 13 in which said means to counta selected number 11 comprises said second counter, said binary ratemultiplier being connected to said down input terminal to count saidnumber n down to zero at a rate f proportional to the number n, and tosaid repetition rate f and inversely proportional to said maximum countn 15. The digital analyzing means of claim 14 in which said means tocount from zero to a number )1, comprises a third counter.

16. The digital analyzing means of claim 15 comprising, in addition:

A. means connecting said clock signal means to said third counter tocount up from zero while said counter is counting said number n down tozero;

B. means to transfer the count from said third counter to said secondcounter when said second counter reaches zero;

C. means to modify the ratio in said binary rate multiplier to producean output signal having a repetition rate f proportional to 3600 f andinversely proportional to n,,, and to cause said counter to count downto zero a second time at said rate f and D. means to connect said clocksignal source means to said third counter to count up from zero to saidnumber n, at said rate f 17. The digital analyzing means of claim 12comprising, in addition:

A. a data register having an input connected to said first counter torecord the number m;

B. a data selector connected to said data register to select either saidnumber n or the number 3600; and

C. means connecting the output of said data selector to said firstcounter to enter said number 3600 into said counter or to reenter saidnumber n into said counter.

18. The digital analyzing means of claim 12 comprising, in addition:

A. means to generate a sweep ramp signal synchronously with said timingpulses; and

B. means comprising a voltage comparator and a reference voltage sourceto generate a mark pulse at any selected point along said ramp and meansto use said mark pulse to initiate the counting of said second number nin said second counter.

19. The process of analyzing angular rotation of a body comprising thesteps of:

A. counting a series of pulses of a first fixed repetition ratef saidcounting beginning when said body reaches a predetermined angularposition and ending when said body again reaches said predeterminedangular position, the number of said pulses counted being defined as nB. subsequently establishing a time interval t, by

counting a selected number n of pulses of said series of pulsesmultiplied by a selected ratio to have a second repetition rate fproportional to said first repetition rate and proportional to thenumber n in said first series and inversely proportional to a maximumcount n,,,, whereby t n n ln f and C. counting a series of clock pulsesfor a time interval that has a duration equal to the time it takes tocount said selected number n of pulses, the repetition rate of saidclock pulses being proportional to the repetition rate of said firstpulses, and said selected number n being proportional to the repetitionrate of said clock pulses such that said lastnamed count n of said clockpulses is a measure of the angular rotation of said body.

20. The process of claim 19 comprising the additional steps of:

A. counting a sub-series n of said first-named pulses at said rate fbeginning after said body has passed said predetermined angular positionand ending when said counting of said series of pulses ends; and

B. selecting'the number n of said pulses of said subseries to count atsaid second rate f,, whereby the number of clock pulses counted duringthe count of said sub-series represents the angle of rotation of saidbody during the counting of said sub-series.

l l l

1. Digital analyzing means for a rotating body, said means comprising:A. clock signal source means to produce fixed repetition rate clocksignals; B. a first counter; C. first connecting means to connect saidfirst counter to said source means to count a first number n1 of saidclock signals at a repetition rate of fc while said body rotates througha first angle; D. a second counter; E. second connecting means toconnect said second counter to said source means to count a secondnumber n2 of said clock signals at a rate of kfc proportional to therepetition rate fc while said body rotates through a second angle; F.first signal generating means connected to said clock signal sourcemeans to generate a first signal having a repetition rate f1proportional to the repetition rate fc and to said number n1 andinversely proportional to a maximum count nm; G. means connected to saidfirst signal-generating means to count a selected number n3 at saidrepetition rate f1 to establish a first time interval t1 n3/f1; H.second signal-generating means connected to said clock signal sourcemeans to generate a second signal having a repetition rate f2; and I.means connected to said second signal-generating means to count fromzero to a number n4 at a rate f2 for said time t1 such that n4 t1f2 is ameasure of angular rotation of said rotating body.
 1. Digital analyzingmeans for a rotating body, said means comprising: A. clock signal sourcemeans to produce fixed repetition rate clock signals; B. a firstcounter; C. first connecting means to connect said first counter to saidsource means to count a first number n1 of said clock signals at arepetition rate of fc while said body rotates through a first angle; D.a second counter; E. second connecting means to connect said secondcounter to said source means to count a second number n2 of said clocksignals at a rate of kfc proportional to the repetition rate fc whilesaid body rotates through a second angle; F. first signal generatingmeans connected to said clock signal source means to generate a firstsignal having a repetition rate f1 proportional to the repetition ratefc and to said number n1 and inversely proportional to a maximum countnm; G. means connected to said first signal-generating means to count aselected number n3 at said repetition rate f1 to establish a first timeinterval t1 n3/f1; H. second signal-generating means connected to saidclock signal source means to generate a second signal having arepetition rate f2; and I. means connected to said secondsignal-generating means to count from zero to a number n4 at a rate f2for said time t1 such that n4 t1f2 is a measure of angular rotation ofsaid rotating body.
 1. means to generate a timing impulse signal eachtime said rotating body passes a predetermined angular position, and 2.The analyzing means of claim 1 in which said first connecting meanscomprises: A. means to generate a timing pulse signal each time saidrotating body passes a predetermined angular position; and B. gatingmeans opened by selected ones of said timing impulse signals and closedby the succeeding timing impulse signal, whereby said first angle is360*.
 2. first gating means opened by selected ones of said timingimpulse signals and closed by the succeeding timing impulse signal,whereby said first angle is 360*; B. said second counter is an up-downcounter comprising an up input terminal and a down input terminal; andC. said second connecting means comprises second gating means opened ata time corresponding to a selected event during a rotation of said bodyand closed simultaneously with said first gating means and connectingsaid clock signal source means to said up input terminal.
 3. The digitalanalyzing means of claim 2 in which k
 1. 4. The digital analyzing meansof claim 3 in which f1 n1/nmfc.
 5. The analyzing means of claim 2 inwhich said selected number n3 is 60fc/nm and said rate f2 isproportional to the rate fc, whereby said number n4 is the number ofrevolutions per minute of said body.
 6. The analyzing means of claim 5in which said means to count from zero to a number n4 comprises a scalercircuit having a scaling ratio r, whereby f2 fc/r.
 7. The analyzingmeans of claim 6 in which r
 100. 8. The digital analyzing means of claim5 in which said means to count a selected number n3 comprises saidsecond counter and said means to count from zero to a number n4comprises a third counter.
 9. The digital analyzing means of claim 8 inwhich said second counter is an up-down counter comprising means toparallel-load said number n3 therein.
 10. The digital analyzing means ofclaim 2 in which: A. said second connecting means comprises secondgating means that opens at a particular point in a revolution of saidbody to start the count of n2 at a particular engine event and closessimultaneously with said first-named gating means; B. n3 n2; and C. f23600fc/nm
 11. The digital analyzing means of claim 1 in which n3 n2 andf2 is proportional to 3600fc and inversely proportional to nm, wherebysaid number n4 is a measure of the angle through which said body rotateswhile said second counter is counting n2.
 12. The digital analyzingmeans of claim 1 in which said first signal-generating means comprises abinary rate multiplier having a maximum count nm higher than any numbern1 or 3600 to be entered into it.
 13. The digital analyzing means ofclaim 12 in which: A. said first connecting means comprises:
 14. Thedigital analyzing means of claim 13 in which said means to count aselected number n3 comprises said second counter, said binary ratemultiplier being connected to said down input terminal to count saidnumber n2 down to zero at a rate f1 proportional to the number n1 and tosaid repetition rate fc and inversely proportional to said maximum countnm.
 15. The digital analyzing means of claim 14 in which said means tocount from zero to a number n4 Comprises a third counter.
 16. Thedigital analyzing means of claim 15 comprising, in addition: A. meansconnecting said clock signal means to said third counter to count upfrom zero while said counter is counting said number n2 down to zero; B.means to transfer the count from said third counter to said secondcounter when said second counter reaches zero; C. means to modify theratio in said binary rate multiplier to produce an output signal havinga repetition rate f2 proportional to 3600 fc and inversely proportionalto nm and to cause said counter to count down to zero a second time atsaid rate f2; and D. means to connect said clock signal source means tosaid third counter to count up from zero to said number n4 at said ratef2.
 17. The digital analyzing means of claim 12 comprising, in addition:A. a data register having an input connected to said first counter torecord the number n1; B. a data selector connected to said data registerto select either said number n1 or the number 3600; and C. meansconnecting the output of said data selector to said first counter toenter said number 3600 into said counter or to reenter said number n1into said counter.
 18. The digital analyzing means of claim 12comprising, in addition: A. means to generate a sweep ramp signalsynchronously with said timing pulses; and B. means comprising a voltagecomparator and a reference voltage source to generate a mark pulse atany selected point along said ramp and means to use said mark pulse toinitiate the counting of said second number n2 in said second counter.19. The process of analyzing angular rotation of a body comprising thesteps of: A. counting a series of pulses of a first fixed repetitionrate fc, said counting beginning when said body reaches a predeterminedangular position and ending when said body again reaches saidpredetermined angular position, the number of said pulses counted beingdefined as n1; B. subsequently establishing a time interval t1 bycounting a selected number n2 of pulses of said series of pulsesmultiplied by a selected ratio to have a second repetition rate f1proportional to said first repetition rate and proportional to thenumber n1 in said first series and inversely proportional to a maximumcount nm, whereby t1 n2nm/n1fc; and C. counting a series of clock pulsesfor a time interval that has a duration equal to the time it takes tocount said selected number n2 of pulses, the repetition rate of saidclock pulses being proportional to the repetition rate of said firstpulses, and said selected number n2 being proportional to the repetitionrate of said clock pulses such that said last-named count n3 of saidclock pulses is a measure of the angular rotation of said body.